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#include "uart.h"
#include "psr.h"
#include "memory.h"
#include "translation_table_descriptors.h"
void demo_paging_support(void)
{
uint32_t ID_MMFR0;
// get contents of coprocessor register to check for paging support
asm("mrc p15, 0, %0, c0, c1, 4" : "=r" (ID_MMFR0));
char *paging;
switch(ID_MMFR0 & 0xf) /* lowest 4 bits indicate VMSA support */
{
case 0 : paging = "no paging\n\r"; break;
case 1 : paging = "implementation defined paging\n\r"; break;
case 2 : paging = "VMSAv6, with cache and TLB type registers\n\r"; break;
case 3 : paging = "VMSAv7, with support for remapping and access flag\n\r"; break;
case 4 : paging = "VMSAv7 with PXN bit supported\n\r"; break;
case 5 : paging = "VMSAv7, PXN and long format descriptors. EPAE is supported.\n\r"; break;
default : paging = "?_? unknown paging ?_?\n\r";
}
uart_puts(paging);
}
void demo_mode_to_system(void)
{
// get content of current program status register to check the current
// processor mode
PSR_t CPSR = read_CPSR();
char *mode_name;
switch(CPSR.fields.PSR_MODE_4_0)
{
case MODE_USER : mode_name = "User (PL0)\r\n"; break;
case MODE_FIQ : mode_name = "FIQ (PL1)\r\n"; break;
case MODE_IRQ : mode_name = "IRQ (PL1)\r\n"; break;
case MODE_SUPERVISOR : mode_name = "Supervisor (PL1)\r\n"; break;
case MODE_MONITOR : mode_name = "Monitor (PL1)\r\n"; break;
case MODE_ABORT : mode_name = "Abort (PL1)\r\n"; break;
case MODE_HYPERVISOR : mode_name = "Hyp (PL2)\r\n"; break;
case MODE_UNDEFINED : mode_name = "Undefined (PL1)\r\n"; break;
case MODE_SYSTEM : mode_name = "System (PL1)\r\n"; break;
default : mode_name = "Unknown mode\r\n"; break;
}
uart_puts("current mode: ");
uart_puts(mode_name);
uart_puts("setting mode to system (PL1)...\r\n");
set_system_mode();
}
extern char
_binary_PL_0_test_img_start,
_binary_PL_0_test_img_end,
_binary_PL_0_test_img_size;
void demo_go_unprivileged(void)
{
short_section_descriptor_t *translation_table =
(short_section_descriptor_t*) TRANSLATION_TABLE_BASE;
volatile short_section_descriptor_t *PL0_code_section =
&translation_table[PL0_SECTION_NUMBER];
volatile short_section_descriptor_t *UART_memory_section =
&translation_table[((uint32_t) GPIO_BASE) >> 20];
PL0_code_section->SECTION_BASE_ADDRESS_31_20 =
UNPRIVILEGED_MEMORY_START >> 20;
// make the selected section and uart section available for PL0
PL0_code_section->ACCESS_PERMISSIONS_2 =
AP_2_0_MODEL_RW_ALL >> 2;
PL0_code_section->ACCESS_PERMISSIONS_1_0 =
AP_2_0_MODEL_RW_ALL & 0b011;
UART_memory_section->ACCESS_PERMISSIONS_2 =
AP_2_0_MODEL_RW_ALL >> 2;
UART_memory_section->ACCESS_PERMISSIONS_1_0 =
AP_2_0_MODEL_RW_ALL & 0b011;
// invalidate main Translation Lookup Buffer (just in case)
asm("mcr p15, 0, %0, c8, c7, 0\n\r"
"isb" :: "r" (0) : "memory");
// check that translation works... by copying a string using one
// mapping and reading it using other :D
char message[] = "mapped sections for PL0 code\n\r";
unsigned int i;
for (i = 0; i < sizeof(message); i++)
((volatile char*) UNPRIVILEGED_MEMORY_START)[i] = message[i];
uart_puts((char*) VIRTUAL_PL0_MEMORY_START);
// now paste a userspace program to that section, jump to it and
// switch to PL0
for (size_t i = 0; i < (size_t) &_binary_PL_0_test_img_size; i++)
((volatile char*) VIRTUAL_PL0_MEMORY_START)[i] =
(&_binary_PL_0_test_img_start)[i];
// jump to that copied code (switch to PL0 is done by that code)
asm volatile("mov r5, #0\n\r"
"movt r5, #"PL0_SECTION_NUMBER_STR"1111\n\r"
"mov sp, r5\n\r" // setting stack is important :D
"mov r5, #0\n\r"
"movt r5, #"PL0_SECTION_NUMBER_STR"0000\n\r"
"blx r5\n\r");
}
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